1. Field of the Invention
The present invention relates to valve actuator and more particularly to a bi-directional rotary apparatus with two hydraulically driven advance levers incrementally driven by a hydraulic system.
2. Description of the Prior Art
U.S. Pat. No. 3,748,915, entitled Multiposition Bi-directional Rotary Means for a Switch or the Like, issued to Ronald C. Winter and Enno A. Knief on July 31, 1973, teaches a multiposition bi-directional rotary means for a switch which includes a rotary ratchet operated by two actuating push levers. Two advance levers or pawls are slidably and pivotally mounted and engage this ratchet from opposite radial directions. Each advance lever has means for engaging the ratchet to rotate the ratchet one step to an adjacent position and means to engage the ratchet and releasably hold it in a position. One lever rotates it in one direction the other lever rotates it the opposite direction. A single spring engages both advance levers to urge them radially inward toward the ratchet. Other springs urge the advance levers or pawls tangentially of the ratchet toward projected at-rest positions. The push levers have projections to engage the advance levers for effecting lineal sliding movement and permitting pivoting of such advance levers relative to the ratchet and the push levers.
U.S. Pat. No. 3,626,452 shows and describes multi-positioned bi-directionary rotary means for a switch or the like which utilizes independent slidably and pivotally mounted spring biased actuating levers or pawls. This patent however does not teach or disclose the use of a single C-shaped spring which urges such actuating levers or pawls radially inwardly toward the rotary ratchet. Neither does this patent utilize a ratchet engaging shape on the actuating levers or pawls which engages two teeth spaced by a third tooth on the ratchet to provide the locking means by one pawl during the retracting action of the other pawl from its ratchet advance position.
U.S. Pat. No. 3,768,775 entitled Portable Valve Actuator, issued to Monte B. Archer on Oct. 30, 1973, teaches a portable valve actuator.
U.S. Pat. No. 3,203,266, entitled Valve Mechanisms, issued to Robert S. Willis and William J. Baker on Aug. 31, 1965, teaches a valve operator for a valve mechanism having a movable valve member, wherein the operator comprises means connected to and moving the valve member by repeated movements of predetermined amount. In case the valve is of the rotary type in which the movement of the valve itself is reversed in moving from closed to opened position and back to closed position, the valve driving member of the valve operator is moved in either one of two directions. The repeated movements being preferably equal and each of a predetermined amount, the algebraic sum of the number of such movements may be used as an indicator of the valve position, making possible the location of the indicator at a position remote from the valve installation.
It is a serious problem in certain types of valves including those of the rotary type, particularly when they are remotely controlled or power operated, to set them at a desired position between the fully opened and closed positions. In each of the latter positions, it is possible to have stop means limiting the valve movement so that the valve stops at a known position in which it is fully opened or closed. However, such stop or limiting means cannot be applied directly to a valve at intermediate or partially open positions because such means would then interfere with movement of the valve beyond the stop means. There are many situations, as for example when a valve is used to meter fluid flow, in which it is necessary that the valve be accurately positioned at some position intermediate its full range of travel, while remaining free to continue movement.
Knowledge of the position of the valve should be readily available at all times and, consequently, it is desirable that the position of the valve should be indicated visually. When the valve is remotely controlled, it is especially desirable that such position indication be present at the remote control station either in addition to or instead of the indicating means located at the valve.
The valve operator of U.S. Pat. No. 3,203,266 may only be used with a multiple orifice-type valve which is fully closed by a turning of its stem of ninety degrees. The use of control valves of the needle and seat type require not only more torque to adjust their flow, but also more revolutions of the stem.